Re: [PATCH v1] gdb/linux: add helpers to read AT_HWCAP3 and AT_HWCAP4

[Simon Marchi <simark@simark.ca>]

On 7/27/26 1:28 PM, Matthieu Longo wrote:
> Add linux_get_hwcap3 and linux_get_hwcap4 helpers to GDB and gdbserver,
> mirroring the existing linux_get_hwcap and linux_get_hwcap2 interfaces.
> 
> The new helpers retrieve the AT_HWCAP3 and AT_HWCAP4 auxiliary vector
> entry either from explicitly supplied auxv data or from the current
> inferior.
> 
> This prepares for future features that depend on HWCAP3 and HWCAP4
> capability bits.
> 
> Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>

LGTM

Approved-By: Simon Marchi <simon.marchi@efficios.com>

But one question that picked my curiosity:

> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
> index f1be62225e2..c4daba0bf40 100644
> --- a/gdbserver/linux-low.cc
> +++ b/gdbserver/linux-low.cc
> @@ -70,6 +70,14 @@
>  #define AT_HWCAP2 26
>  #endif
>  
> +#ifndef AT_HWCAP3
> +#define AT_HWCAP3 29
> +#endif
> +
> +#ifndef AT_HWCAP4
> +#define AT_HWCAP4 30
> +#endif

How come we need to provide these values in gdbserver, but not in the
equivalent native part of gdb?

Simon